Newbie needs help understanding screw mapping and backlash compensation

I'm pretty new to CNC (having only built a GRBL/Arduino router recently) and I'm working on converting my RF30 mill to CNC. I have bluetooth DRO on the mill so backlash was never really an issue for me. However, with CNC I'm wondering how to compensate for the backlash (let's say it's .0125" on the X and Y axis). Can I put .0125 somewhere in the .ini file? I know there's also something called screw mapping, is this the same thing? would that be a better way to do this and other than this man page wiki.linuxcnc.org/cgi-bin/wiki.pl?Screw_Compensation is there a slightly more detailed explanation or examples of how to configure this? Apologies if this has been beaten to death before- I'm looking around here but not having a lot of luck finding prior posted info.

Yes there is a setting for Backlash Compensation in the INI file. It is in the Axis section (or Joint in Master).
linuxcnc.org/docs/2.7/html/config/ini-co...s__lt_num_gt_section

However .0125 is a rather large amount to try to compensate for. I would recommend trying to reduce the backlash mechanically as much as you can.

Screw mapping is a different form of compensation that is designed to overcome inaccuracies of your screw. (I've never tried to use it.)

Cool, thanks Todd. I think you and I found the backlash parameter about the same time. I found mine via Google here: www.britishideas.com/2008/06/19/measurin...ftware-compensation/

I don't know what the actual backlash is, I'll measure it soon. It's an old RF30 mill, but even at .0125" that's less than half a mm and for me (hobby stuff) that's good enough for govt work

Hi sitoc
Have been living with backlash quite some years, just modified as Christmas present to myself to ballscrews. Linuxcnc does nice compensation but can not overcome the problem that your mills makes chatter marks as your peace is moved for/backwards by each tooth. So adjust play to your best to get nicer surfaces.
Mike

Thanks Mike, I completely agree. However, I'm doing this in stages- for now I'm just trying to get close enough with what I've got, I'm not doing any precise work. I'll tackle the ballscrews in the future as another project. Now adjusting the gibs etc I should do that. Having never done it before I've been avoiding it but I'm youtube certified in everything lol.

When i disassembled my mill i saw that there have been tiny screws to tighten the screwnuts.
Maybe you find something similar too.
I'm aware that this admission will project a smile on faces of the true mechanics guys here on the list
Mike